[PATCH v3] usb: cdnsp: Add support for device-only configuration

[PATCH v3] usb: cdnsp: Add support for device-only configuration

[Pawel Laszczak via B4 Relay]

From: Pawel Laszczak <pawell@cadence.com>

This patch introduces support for the Cadence USBSSP (cdnsp)
controller in hardware configurations where the Dual-Role Device (DRD)
register block is not implemented or is inaccessible.

In such cases, the driver cannot rely on the DRD logic to manage roles
and must operate exclusively in a fixed peripheral/host mode.

The change in BAR indexing (from BAR 2 to BAR 1) is a direct
consequence of the 32-bit addressing used in this specific
DRD-disabled hardware layout, compared to the 64-bit addressing
used in DRD-enabled configurations.

Tested on a PCI platform with a hardware configuration that lacks
DRD support. Platform-side changes are included to support the PCI
glue layer's property injection to handle this specific layout.

Acked-by: Bjorn Helgaas <bhelgaas@google.com> # pci_ids.h
Signed-off-by: Pawel Laszczak <pawell@cadence.com>
---
v3:
  - Improved descriptions and comments for better clarity.
  - Introduced the 'no_drd' property to indicate missing DRD register block.
  - Added support for fixed host-only and device-only configurations.
  - Ensured cdns_otg_disable_irq is called only when no_drd is false.
  - Updated cdns_drd_gadget_on/off to ensure PHY mode is correctly 
    handled even if DRD is disabled.

v2:
  - Changed otg_irq to be optionali.
  - Added cdns->no_drd check in cdns_power_is_lost.
  - Added cdns->no_drd check in cdns_get_id.
---
 drivers/usb/cdns3/cdns3-plat.c | 26 ++++++++++++++----------
 drivers/usb/cdns3/cdnsp-pci.c  | 46 +++++++++++++++++++++++++++++++++---------
 drivers/usb/cdns3/core.c       |  3 ++-
 drivers/usb/cdns3/core.h       |  4 ++++
 drivers/usb/cdns3/drd.c        | 44 ++++++++++++++++++++++++++++++++++++++--
 include/linux/pci_ids.h        |  1 +
 6 files changed, 101 insertions(+), 23 deletions(-)

diff --git a/drivers/usb/cdns3/cdns3-plat.c b/drivers/usb/cdns3/cdns3-plat.c
index 3fe3109a3688..86c963a072db 100644
--- a/drivers/usb/cdns3/cdns3-plat.c
+++ b/drivers/usb/cdns3/cdns3-plat.c
@@ -81,6 +81,7 @@ static int cdns3_plat_probe(struct platform_device *pdev)
 	if (cdns->pdata && cdns->pdata->override_apb_timeout)
 		cdns->override_apb_timeout = cdns->pdata->override_apb_timeout;
 
+	cdns->no_drd = device_property_read_bool(dev, "no_drd");
 	platform_set_drvdata(pdev, cdns);
 
 	ret = platform_get_irq_byname(pdev, "host");
@@ -113,21 +114,24 @@ static int cdns3_plat_probe(struct platform_device *pdev)
 
 	cdns->dev_regs	= regs;
 
-	cdns->otg_irq = platform_get_irq_byname(pdev, "otg");
-	if (cdns->otg_irq < 0)
-		return dev_err_probe(dev, cdns->otg_irq,
-				     "Failed to get otg IRQ\n");
-
-	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "otg");
-	if (!res) {
-		dev_err(dev, "couldn't get otg resource\n");
-		return -ENXIO;
+	if (!cdns->no_drd) {
+		cdns->otg_irq = platform_get_irq_byname(pdev, "otg");
+		if (cdns->otg_irq < 0)
+			return dev_err_probe(dev, cdns->otg_irq,
+					     "Failed to get otg IRQ\n");
+
+		res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "otg");
+		if (!res) {
+			dev_err(dev, "couldn't get otg resource\n");
+			return -ENXIO;
+		}
+		cdns->otg_res = *res;
+	} else {
+		dev_dbg(dev, "No DRD support\n");
 	}
 
 	cdns->phyrst_a_enable = device_property_read_bool(dev, "cdns,phyrst-a-enable");
 
-	cdns->otg_res = *res;
-
 	cdns->wakeup_irq = platform_get_irq_byname_optional(pdev, "wakeup");
 	if (cdns->wakeup_irq == -EPROBE_DEFER)
 		return cdns->wakeup_irq;
diff --git a/drivers/usb/cdns3/cdnsp-pci.c b/drivers/usb/cdns3/cdnsp-pci.c
index 432007cfe695..992700479172 100644
--- a/drivers/usb/cdns3/cdnsp-pci.c
+++ b/drivers/usb/cdns3/cdnsp-pci.c
@@ -19,6 +19,7 @@
 
 struct cdnsp_wrap {
 	struct platform_device *plat_dev;
+	struct property_entry prop[3];
 	struct resource dev_res[6];
 	int devfn;
 };
@@ -29,10 +30,15 @@ struct cdnsp_wrap {
 #define RES_HOST_ID		3
 #define RES_DEV_ID		4
 #define RES_DRD_ID		5
-
+/* DRD PCI configuration - 64-bit addressing */
+/* First PCI function */
 #define PCI_BAR_HOST		0
-#define PCI_BAR_OTG		0
 #define PCI_BAR_DEV		2
+/* Second PCI function */
+#define PCI_BAR_OTG		0
+/* Device only PCI configuration - 32-bit addressing */
+/* First PCI function */
+#define PCI_BAR_ONLY_DEV	1
 
 #define PCI_DEV_FN_HOST_DEVICE	0
 #define PCI_DEV_FN_OTG		1
@@ -65,6 +71,7 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
 	struct cdnsp_wrap *wrap;
 	struct resource *res;
 	struct pci_dev *func;
+	bool no_drd = false;
 	int ret = 0;
 
 	/*
@@ -75,11 +82,14 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
 		    pdev->devfn != PCI_DEV_FN_OTG))
 		return -EINVAL;
 
+	if (pdev->device == PCI_DEVICE_ID_CDNS_UDC_USBSSP)
+		no_drd = true;
+
 	func = cdnsp_get_second_fun(pdev);
-	if (!func)
+	if (!func && !no_drd)
 		return -EINVAL;
 
-	if (func->class == PCI_CLASS_SERIAL_USB_XHCI ||
+	if ((func && func->class == PCI_CLASS_SERIAL_USB_XHCI) ||
 	    pdev->class == PCI_CLASS_SERIAL_USB_XHCI) {
 		ret = -EINVAL;
 		goto put_pci;
@@ -93,7 +103,7 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
 
 	pci_set_master(pdev);
 
-	if (pci_is_enabled(func)) {
+	if (func && pci_is_enabled(func)) {
 		wrap = pci_get_drvdata(func);
 	} else {
 		wrap = kzalloc_obj(*wrap);
@@ -106,10 +116,12 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
 	res = wrap->dev_res;
 
 	if (pdev->devfn == PCI_DEV_FN_HOST_DEVICE) {
+		int bar_dev = no_drd ? PCI_BAR_ONLY_DEV : PCI_BAR_DEV;
+
 		/* Function 0: host(BAR_0) + device(BAR_2). */
 		dev_dbg(&pdev->dev, "Initialize Device resources\n");
-		res[RES_DEV_ID].start = pci_resource_start(pdev, PCI_BAR_DEV);
-		res[RES_DEV_ID].end = pci_resource_end(pdev, PCI_BAR_DEV);
+		res[RES_DEV_ID].start = pci_resource_start(pdev, bar_dev);
+		res[RES_DEV_ID].end = pci_resource_end(pdev, bar_dev);
 		res[RES_DEV_ID].name = "dev";
 		res[RES_DEV_ID].flags = IORESOURCE_MEM;
 		dev_dbg(&pdev->dev, "USBSSP-DEV physical base addr: %pa\n",
@@ -145,9 +157,20 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
 		wrap->dev_res[RES_IRQ_OTG_ID].flags = IORESOURCE_IRQ;
 	}
 
-	if (pci_is_enabled(func)) {
+	if (no_drd || pci_is_enabled(func)) {
+		u8 idx = 0;
+
 		/* set up platform device info */
 		pdata.override_apb_timeout = CHICKEN_APB_TIMEOUT_VALUE;
+
+		if (no_drd) {
+			wrap->prop[idx++] = PROPERTY_ENTRY_STRING("dr_mode", "peripheral");
+			wrap->prop[idx++] = PROPERTY_ENTRY_BOOL("no_drd");
+		} else {
+			wrap->prop[idx++] = PROPERTY_ENTRY_STRING("dr_mode", "otg");
+			wrap->prop[idx++] = PROPERTY_ENTRY_BOOL("usb-role-switch");
+		}
+
 		memset(&plat_info, 0, sizeof(plat_info));
 		plat_info.parent = &pdev->dev;
 		plat_info.fwnode = pdev->dev.fwnode;
@@ -158,6 +181,7 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
 		plat_info.dma_mask = pdev->dma_mask;
 		plat_info.data = &pdata;
 		plat_info.size_data = sizeof(pdata);
+		plat_info.properties = wrap->prop;
 		wrap->devfn = pdev->devfn;
 		/* register platform device */
 		wrap->plat_dev = platform_device_register_full(&plat_info);
@@ -185,13 +209,17 @@ static void cdnsp_pci_remove(struct pci_dev *pdev)
 	if (wrap->devfn == pdev->devfn)
 		platform_device_unregister(wrap->plat_dev);
 
-	if (!pci_is_enabled(func))
+	if (!func || !pci_is_enabled(func))
 		kfree(wrap);
 
 	pci_dev_put(func);
 }
 
 static const struct pci_device_id cdnsp_pci_ids[] = {
+	{ PCI_DEVICE(PCI_VENDOR_ID_CDNS, PCI_DEVICE_ID_CDNS_UDC_USBSSP),
+	  .class = PCI_CLASS_SERIAL_USB_DEVICE },
+	{ PCI_DEVICE(PCI_VENDOR_ID_CDNS, PCI_DEVICE_ID_CDNS_UDC_USBSSP),
+	  .class = PCI_CLASS_SERIAL_USB_CDNS },
 	{ PCI_DEVICE(PCI_VENDOR_ID_CDNS, PCI_DEVICE_ID_CDNS_USBSSP),
 	  .class = PCI_CLASS_SERIAL_USB_DEVICE },
 	{ PCI_DEVICE(PCI_VENDOR_ID_CDNS, PCI_DEVICE_ID_CDNS_USBSSP),
diff --git a/drivers/usb/cdns3/core.c b/drivers/usb/cdns3/core.c
index 6a8d1fefbc0d..504bdf13ea80 100644
--- a/drivers/usb/cdns3/core.c
+++ b/drivers/usb/cdns3/core.c
@@ -70,7 +70,8 @@ static void cdns_role_stop(struct cdns *cdns)
 static void cdns_exit_roles(struct cdns *cdns)
 {
 	cdns_role_stop(cdns);
-	cdns_drd_exit(cdns);
+	if (!cdns->no_drd)
+		cdns_drd_exit(cdns);
 }
 
 /**
diff --git a/drivers/usb/cdns3/core.h b/drivers/usb/cdns3/core.h
index bca973b999a4..8c492fda924c 100644
--- a/drivers/usb/cdns3/core.h
+++ b/drivers/usb/cdns3/core.h
@@ -84,6 +84,9 @@ struct cdns3_platform_data {
  *                        value in CHICKEN_BITS_3 will be preserved.
  * @gadget_init: pointer to gadget initialization function
  * @host_init: pointer to host initialization function
+ * @no_drd: DRD register block is inaccessible. The controller is hardwired to
+ *          single role (host or device) or the logic for role switching is
+ *          missing.
  */
 struct cdns {
 	struct device			*dev;
@@ -124,6 +127,7 @@ struct cdns {
 	u32                             override_apb_timeout;
 	int (*gadget_init)(struct cdns *cdns);
 	int (*host_init)(struct cdns *cdns);
+	bool				no_drd;
 };
 
 int cdns_hw_role_switch(struct cdns *cdns);
diff --git a/drivers/usb/cdns3/drd.c b/drivers/usb/cdns3/drd.c
index 84fb38a5723a..f87cf85cb97a 100644
--- a/drivers/usb/cdns3/drd.c
+++ b/drivers/usb/cdns3/drd.c
@@ -87,6 +87,9 @@ int cdns_get_id(struct cdns *cdns)
 {
 	int id;
 
+	if (cdns->no_drd)
+		return 0;
+
 	id = readl(&cdns->otg_regs->sts) & OTGSTS_ID_VALUE;
 	dev_dbg(cdns->dev, "OTG ID: %d", id);
 
@@ -107,7 +110,7 @@ void cdns_clear_vbus(struct cdns *cdns)
 {
 	u32 reg;
 
-	if (cdns->version != CDNSP_CONTROLLER_V2)
+	if (cdns->version != CDNSP_CONTROLLER_V2 || cdns->no_drd)
 		return;
 
 	reg = readl(&cdns->otg_cdnsp_regs->override);
@@ -120,7 +123,7 @@ void cdns_set_vbus(struct cdns *cdns)
 {
 	u32 reg;
 
-	if (cdns->version != CDNSP_CONTROLLER_V2)
+	if (cdns->version != CDNSP_CONTROLLER_V2 || cdns->no_drd)
 		return;
 
 	reg = readl(&cdns->otg_cdnsp_regs->override);
@@ -181,6 +184,9 @@ int cdns_drd_host_on(struct cdns *cdns)
 	u32 val, ready_bit;
 	int ret;
 
+	if (cdns->no_drd)
+		goto phy_set;
+
 	/* Enable host mode. */
 	writel(OTGCMD_HOST_BUS_REQ | OTGCMD_OTG_DIS,
 	       &cdns->otg_regs->cmd);
@@ -197,6 +203,7 @@ int cdns_drd_host_on(struct cdns *cdns)
 	if (ret)
 		dev_err(cdns->dev, "timeout waiting for xhci_ready\n");
 
+phy_set:
 	phy_set_mode(cdns->usb2_phy, PHY_MODE_USB_HOST);
 	phy_set_mode(cdns->usb3_phy, PHY_MODE_USB_HOST);
 	return ret;
@@ -210,6 +217,9 @@ void cdns_drd_host_off(struct cdns *cdns)
 {
 	u32 val;
 
+	if (cdns->no_drd)
+		goto phy_set;
+
 	writel(OTGCMD_HOST_BUS_DROP | OTGCMD_DEV_BUS_DROP |
 	       OTGCMD_DEV_POWER_OFF | OTGCMD_HOST_POWER_OFF,
 	       &cdns->otg_regs->cmd);
@@ -218,6 +228,8 @@ void cdns_drd_host_off(struct cdns *cdns)
 	readl_poll_timeout_atomic(&cdns->otg_regs->state, val,
 				  !(val & OTGSTATE_HOST_STATE_MASK),
 				  1, 2000000);
+
+phy_set:
 	phy_set_mode(cdns->usb2_phy, PHY_MODE_INVALID);
 	phy_set_mode(cdns->usb3_phy, PHY_MODE_INVALID);
 }
@@ -234,6 +246,9 @@ int cdns_drd_gadget_on(struct cdns *cdns)
 	u32 ready_bit;
 	int ret, val;
 
+	if (cdns->no_drd)
+		goto phy_set;
+
 	/* switch OTG core */
 	writel(OTGCMD_DEV_BUS_REQ | reg, &cdns->otg_regs->cmd);
 
@@ -251,6 +266,7 @@ int cdns_drd_gadget_on(struct cdns *cdns)
 		return ret;
 	}
 
+phy_set:
 	phy_set_mode(cdns->usb2_phy, PHY_MODE_USB_DEVICE);
 	phy_set_mode(cdns->usb3_phy, PHY_MODE_USB_DEVICE);
 	return 0;
@@ -265,6 +281,9 @@ void cdns_drd_gadget_off(struct cdns *cdns)
 {
 	u32 val;
 
+	if (cdns->no_drd)
+		goto phy_set;
+
 	/*
 	 * Driver should wait at least 10us after disabling Device
 	 * before turning-off Device (DEV_BUS_DROP).
@@ -277,6 +296,8 @@ void cdns_drd_gadget_off(struct cdns *cdns)
 	readl_poll_timeout_atomic(&cdns->otg_regs->state, val,
 				  !(val & OTGSTATE_DEV_STATE_MASK),
 				  1, 2000000);
+
+phy_set:
 	phy_set_mode(cdns->usb2_phy, PHY_MODE_INVALID);
 	phy_set_mode(cdns->usb3_phy, PHY_MODE_INVALID);
 }
@@ -392,6 +413,19 @@ int cdns_drd_init(struct cdns *cdns)
 	u32 state, reg;
 	int ret;
 
+	if (cdns->no_drd) {
+		cdns->dr_mode = usb_get_dr_mode(cdns->dev);
+		cdns->version = CDNSP_CONTROLLER_V2;
+
+		if (cdns->dr_mode != USB_DR_MODE_HOST &&
+		    cdns->dr_mode != USB_DR_MODE_PERIPHERAL) {
+			dev_err(cdns->dev, "Incorrect dr_mode\n");
+			return -EINVAL;
+		}
+
+		return 0;
+	}
+
 	regs = devm_ioremap_resource(cdns->dev, &cdns->otg_res);
 	if (IS_ERR(regs))
 		return PTR_ERR(regs);
@@ -492,6 +526,9 @@ int cdns_drd_init(struct cdns *cdns)
 
 int cdns_drd_exit(struct cdns *cdns)
 {
+	if (cdns->no_drd)
+		return 0;
+
 	cdns_otg_disable_irq(cdns);
 
 	return 0;
@@ -500,6 +537,9 @@ int cdns_drd_exit(struct cdns *cdns)
 /* Indicate the cdns3 core was power lost before */
 bool cdns_power_is_lost(struct cdns *cdns)
 {
+	if (cdns->no_drd)
+		return false;
+
 	if (cdns->version == CDNS3_CONTROLLER_V0) {
 		if (!(readl(&cdns->otg_v0_regs->simulate) & BIT(0)))
 			return true;
diff --git a/include/linux/pci_ids.h b/include/linux/pci_ids.h
index 24cb42f66e4b..a6b9b6f6d8cc 100644
--- a/include/linux/pci_ids.h
+++ b/include/linux/pci_ids.h
@@ -2424,6 +2424,7 @@
 #define PCI_DEVICE_ID_CDNS_USBSS	0x0100
 #define PCI_DEVICE_ID_CDNS_USB		0x0120
 #define PCI_DEVICE_ID_CDNS_USBSSP	0x0200
+#define PCI_DEVICE_ID_CDNS_UDC_USBSSP	0x0400
 
 #define PCI_VENDOR_ID_ARECA		0x17d3
 #define PCI_DEVICE_ID_ARECA_1110	0x1110

---
base-commit: 17c7841d09ee7d33557fd075562d9289b6018c90
change-id: 20260508-no_drd_config-ea76d1df87a3

Best regards,
--  
Pawel Laszczak <pawell@cadence.com>

Re: [PATCH v3] usb: cdnsp: Add support for device-only configuration

[Bjorn Helgaas]

On Fri, May 08, 2026 at 12:06:39PM +0200, Pawel Laszczak via B4 Relay wrote:
> From: Pawel Laszczak <pawell@cadence.com>
> 
> This patch introduces support for the Cadence USBSSP (cdnsp)
> controller in hardware configurations where the Dual-Role Device (DRD)
> register block is not implemented or is inaccessible.
> 
> In such cases, the driver cannot rely on the DRD logic to manage roles
> and must operate exclusively in a fixed peripheral/host mode.
> 
> The change in BAR indexing (from BAR 2 to BAR 1) is a direct
> consequence of the 32-bit addressing used in this specific
> DRD-disabled hardware layout, compared to the 64-bit addressing
> used in DRD-enabled configurations.
> 
> Tested on a PCI platform with a hardware configuration that lacks
> DRD support. Platform-side changes are included to support the PCI
> glue layer's property injection to handle this specific layout.
> 
> Acked-by: Bjorn Helgaas <bhelgaas@google.com> # pci_ids.h

I did ack this
(https://lore.kernel.org/linux-pci/20260331181209.GA148250@bhelgaas/) but I
wish I had added a note about why.  Usually we don't add things to
pci_ids.h unless they're used by more than one driver.  This (slightly)
simplifies backporting things.

Fine as-is, but if you respin for other reasons, you could consider moving
it to cdnsp-pci.c.

> +++ b/include/linux/pci_ids.h

 *      Do not add new entries to this file unless the definitions
 *      are shared between multiple drivers.
 */

> +#define PCI_DEVICE_ID_CDNS_UDC_USBSSP	0x0400

Looks like this #define could go in cdnsp-pci.c, since that's the only
place it's used.

Re: [PATCH v3] usb: cdnsp: Add support for device-only configuration

[Peter Chen (CIX)]

On 26-05-08 12:06:39, Pawel Laszczak via B4 Relay wrote:
> From: Pawel Laszczak <pawell@cadence.com>
> 
> This patch introduces support for the Cadence USBSSP (cdnsp)
> controller in hardware configurations where the Dual-Role Device (DRD)
> register block is not implemented or is inaccessible.
> 
> In such cases, the driver cannot rely on the DRD logic to manage roles
> and must operate exclusively in a fixed peripheral/host mode.
> 
> The change in BAR indexing (from BAR 2 to BAR 1) is a direct
> consequence of the 32-bit addressing used in this specific
> DRD-disabled hardware layout, compared to the 64-bit addressing
> used in DRD-enabled configurations.
> 
> Tested on a PCI platform with a hardware configuration that lacks
> DRD support. Platform-side changes are included to support the PCI
> glue layer's property injection to handle this specific layout.
> 
> Acked-by: Bjorn Helgaas <bhelgaas@google.com> # pci_ids.h
> Signed-off-by: Pawel Laszczak <pawell@cadence.com>
> ---
> v3:
>   - Improved descriptions and comments for better clarity.
>   - Introduced the 'no_drd' property to indicate missing DRD register block.
>   - Added support for fixed host-only and device-only configurations.
>   - Ensured cdns_otg_disable_irq is called only when no_drd is false.
>   - Updated cdns_drd_gadget_on/off to ensure PHY mode is correctly 
>     handled even if DRD is disabled.
> 
> v2:
>   - Changed otg_irq to be optionali.
>   - Added cdns->no_drd check in cdns_power_is_lost.
>   - Added cdns->no_drd check in cdns_get_id.
> ---
>  drivers/usb/cdns3/cdns3-plat.c | 26 ++++++++++++++----------
>  drivers/usb/cdns3/cdnsp-pci.c  | 46 +++++++++++++++++++++++++++++++++---------
>  drivers/usb/cdns3/core.c       |  3 ++-
>  drivers/usb/cdns3/core.h       |  4 ++++
>  drivers/usb/cdns3/drd.c        | 44 ++++++++++++++++++++++++++++++++++++++--

For cdns3 changes:

Acked-by: Peter Chen <peter.chen@kernel.org>

>  include/linux/pci_ids.h        |  1 +
>  6 files changed, 101 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/usb/cdns3/cdns3-plat.c b/drivers/usb/cdns3/cdns3-plat.c
> index 3fe3109a3688..86c963a072db 100644
> --- a/drivers/usb/cdns3/cdns3-plat.c
> +++ b/drivers/usb/cdns3/cdns3-plat.c
> @@ -81,6 +81,7 @@ static int cdns3_plat_probe(struct platform_device *pdev)
>  	if (cdns->pdata && cdns->pdata->override_apb_timeout)
>  		cdns->override_apb_timeout = cdns->pdata->override_apb_timeout;
>  
> +	cdns->no_drd = device_property_read_bool(dev, "no_drd");

When introduce a new property, please update binding doc accordingly.

Peter

> diff --git a/drivers/usb/cdns3/cdnsp-pci.c b/drivers/usb/cdns3/cdnsp-pci.c
> index 432007cfe695..992700479172 100644
> --- a/drivers/usb/cdns3/cdnsp-pci.c
> +++ b/drivers/usb/cdns3/cdnsp-pci.c
> @@ -19,6 +19,7 @@
>  
>  struct cdnsp_wrap {
>  	struct platform_device *plat_dev;
> +	struct property_entry prop[3];
>  	struct resource dev_res[6];
>  	int devfn;
>  };
> @@ -29,10 +30,15 @@ struct cdnsp_wrap {
>  #define RES_HOST_ID		3
>  #define RES_DEV_ID		4
>  #define RES_DRD_ID		5
> -
> +/* DRD PCI configuration - 64-bit addressing */
> +/* First PCI function */
>  #define PCI_BAR_HOST		0
> -#define PCI_BAR_OTG		0
>  #define PCI_BAR_DEV		2
> +/* Second PCI function */
> +#define PCI_BAR_OTG		0
> +/* Device only PCI configuration - 32-bit addressing */
> +/* First PCI function */
> +#define PCI_BAR_ONLY_DEV	1
>  
>  #define PCI_DEV_FN_HOST_DEVICE	0
>  #define PCI_DEV_FN_OTG		1
> @@ -65,6 +71,7 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
>  	struct cdnsp_wrap *wrap;
>  	struct resource *res;
>  	struct pci_dev *func;
> +	bool no_drd = false;
>  	int ret = 0;
>  
>  	/*
> @@ -75,11 +82,14 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
>  		    pdev->devfn != PCI_DEV_FN_OTG))
>  		return -EINVAL;
>  
> +	if (pdev->device == PCI_DEVICE_ID_CDNS_UDC_USBSSP)
> +		no_drd = true;
> +
>  	func = cdnsp_get_second_fun(pdev);
> -	if (!func)
> +	if (!func && !no_drd)
>  		return -EINVAL;
>  
> -	if (func->class == PCI_CLASS_SERIAL_USB_XHCI ||
> +	if ((func && func->class == PCI_CLASS_SERIAL_USB_XHCI) ||
>  	    pdev->class == PCI_CLASS_SERIAL_USB_XHCI) {
>  		ret = -EINVAL;
>  		goto put_pci;
> @@ -93,7 +103,7 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
>  
>  	pci_set_master(pdev);
>  
> -	if (pci_is_enabled(func)) {
> +	if (func && pci_is_enabled(func)) {
>  		wrap = pci_get_drvdata(func);
>  	} else {
>  		wrap = kzalloc_obj(*wrap);
> @@ -106,10 +116,12 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
>  	res = wrap->dev_res;
>  
>  	if (pdev->devfn == PCI_DEV_FN_HOST_DEVICE) {
> +		int bar_dev = no_drd ? PCI_BAR_ONLY_DEV : PCI_BAR_DEV;
> +
>  		/* Function 0: host(BAR_0) + device(BAR_2). */
>  		dev_dbg(&pdev->dev, "Initialize Device resources\n");
> -		res[RES_DEV_ID].start = pci_resource_start(pdev, PCI_BAR_DEV);
> -		res[RES_DEV_ID].end = pci_resource_end(pdev, PCI_BAR_DEV);
> +		res[RES_DEV_ID].start = pci_resource_start(pdev, bar_dev);
> +		res[RES_DEV_ID].end = pci_resource_end(pdev, bar_dev);
>  		res[RES_DEV_ID].name = "dev";
>  		res[RES_DEV_ID].flags = IORESOURCE_MEM;
>  		dev_dbg(&pdev->dev, "USBSSP-DEV physical base addr: %pa\n",
> @@ -145,9 +157,20 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
>  		wrap->dev_res[RES_IRQ_OTG_ID].flags = IORESOURCE_IRQ;
>  	}
>  
> -	if (pci_is_enabled(func)) {
> +	if (no_drd || pci_is_enabled(func)) {
> +		u8 idx = 0;
> +
>  		/* set up platform device info */
>  		pdata.override_apb_timeout = CHICKEN_APB_TIMEOUT_VALUE;
> +
> +		if (no_drd) {
> +			wrap->prop[idx++] = PROPERTY_ENTRY_STRING("dr_mode", "peripheral");
> +			wrap->prop[idx++] = PROPERTY_ENTRY_BOOL("no_drd");
> +		} else {
> +			wrap->prop[idx++] = PROPERTY_ENTRY_STRING("dr_mode", "otg");
> +			wrap->prop[idx++] = PROPERTY_ENTRY_BOOL("usb-role-switch");
> +		}
> +
>  		memset(&plat_info, 0, sizeof(plat_info));
>  		plat_info.parent = &pdev->dev;
>  		plat_info.fwnode = pdev->dev.fwnode;
> @@ -158,6 +181,7 @@ static int cdnsp_pci_probe(struct pci_dev *pdev,
>  		plat_info.dma_mask = pdev->dma_mask;
>  		plat_info.data = &pdata;
>  		plat_info.size_data = sizeof(pdata);
> +		plat_info.properties = wrap->prop;
>  		wrap->devfn = pdev->devfn;
>  		/* register platform device */
>  		wrap->plat_dev = platform_device_register_full(&plat_info);
> @@ -185,13 +209,17 @@ static void cdnsp_pci_remove(struct pci_dev *pdev)
>  	if (wrap->devfn == pdev->devfn)
>  		platform_device_unregister(wrap->plat_dev);
>  
> -	if (!pci_is_enabled(func))
> +	if (!func || !pci_is_enabled(func))
>  		kfree(wrap);
>  
>  	pci_dev_put(func);
>  }
>  
>  static const struct pci_device_id cdnsp_pci_ids[] = {
> +	{ PCI_DEVICE(PCI_VENDOR_ID_CDNS, PCI_DEVICE_ID_CDNS_UDC_USBSSP),
> +	  .class = PCI_CLASS_SERIAL_USB_DEVICE },
> +	{ PCI_DEVICE(PCI_VENDOR_ID_CDNS, PCI_DEVICE_ID_CDNS_UDC_USBSSP),
> +	  .class = PCI_CLASS_SERIAL_USB_CDNS },
>  	{ PCI_DEVICE(PCI_VENDOR_ID_CDNS, PCI_DEVICE_ID_CDNS_USBSSP),
>  	  .class = PCI_CLASS_SERIAL_USB_DEVICE },
>  	{ PCI_DEVICE(PCI_VENDOR_ID_CDNS, PCI_DEVICE_ID_CDNS_USBSSP),
> diff --git a/drivers/usb/cdns3/core.c b/drivers/usb/cdns3/core.c
> index 6a8d1fefbc0d..504bdf13ea80 100644
> --- a/drivers/usb/cdns3/core.c
> +++ b/drivers/usb/cdns3/core.c
> @@ -70,7 +70,8 @@ static void cdns_role_stop(struct cdns *cdns)
>  static void cdns_exit_roles(struct cdns *cdns)
>  {
>  	cdns_role_stop(cdns);
> -	cdns_drd_exit(cdns);
> +	if (!cdns->no_drd)
> +		cdns_drd_exit(cdns);
>  }
>  
>  /**
> diff --git a/drivers/usb/cdns3/core.h b/drivers/usb/cdns3/core.h
> index bca973b999a4..8c492fda924c 100644
> --- a/drivers/usb/cdns3/core.h
> +++ b/drivers/usb/cdns3/core.h
> @@ -84,6 +84,9 @@ struct cdns3_platform_data {
>   *                        value in CHICKEN_BITS_3 will be preserved.
>   * @gadget_init: pointer to gadget initialization function
>   * @host_init: pointer to host initialization function
> + * @no_drd: DRD register block is inaccessible. The controller is hardwired to
> + *          single role (host or device) or the logic for role switching is
> + *          missing.
>   */
>  struct cdns {
>  	struct device			*dev;
> @@ -124,6 +127,7 @@ struct cdns {
>  	u32                             override_apb_timeout;
>  	int (*gadget_init)(struct cdns *cdns);
>  	int (*host_init)(struct cdns *cdns);
> +	bool				no_drd;
>  };
>  
>  int cdns_hw_role_switch(struct cdns *cdns);
> diff --git a/drivers/usb/cdns3/drd.c b/drivers/usb/cdns3/drd.c
> index 84fb38a5723a..f87cf85cb97a 100644
> --- a/drivers/usb/cdns3/drd.c
> +++ b/drivers/usb/cdns3/drd.c
> @@ -87,6 +87,9 @@ int cdns_get_id(struct cdns *cdns)
>  {
>  	int id;
>  
> +	if (cdns->no_drd)
> +		return 0;
> +
>  	id = readl(&cdns->otg_regs->sts) & OTGSTS_ID_VALUE;
>  	dev_dbg(cdns->dev, "OTG ID: %d", id);
>  
> @@ -107,7 +110,7 @@ void cdns_clear_vbus(struct cdns *cdns)
>  {
>  	u32 reg;
>  
> -	if (cdns->version != CDNSP_CONTROLLER_V2)
> +	if (cdns->version != CDNSP_CONTROLLER_V2 || cdns->no_drd)
>  		return;
>  
>  	reg = readl(&cdns->otg_cdnsp_regs->override);
> @@ -120,7 +123,7 @@ void cdns_set_vbus(struct cdns *cdns)
>  {
>  	u32 reg;
>  
> -	if (cdns->version != CDNSP_CONTROLLER_V2)
> +	if (cdns->version != CDNSP_CONTROLLER_V2 || cdns->no_drd)
>  		return;
>  
>  	reg = readl(&cdns->otg_cdnsp_regs->override);
> @@ -181,6 +184,9 @@ int cdns_drd_host_on(struct cdns *cdns)
>  	u32 val, ready_bit;
>  	int ret;
>  
> +	if (cdns->no_drd)
> +		goto phy_set;
> +
>  	/* Enable host mode. */
>  	writel(OTGCMD_HOST_BUS_REQ | OTGCMD_OTG_DIS,
>  	       &cdns->otg_regs->cmd);
> @@ -197,6 +203,7 @@ int cdns_drd_host_on(struct cdns *cdns)
>  	if (ret)
>  		dev_err(cdns->dev, "timeout waiting for xhci_ready\n");
>  
> +phy_set:
>  	phy_set_mode(cdns->usb2_phy, PHY_MODE_USB_HOST);
>  	phy_set_mode(cdns->usb3_phy, PHY_MODE_USB_HOST);
>  	return ret;
> @@ -210,6 +217,9 @@ void cdns_drd_host_off(struct cdns *cdns)
>  {
>  	u32 val;
>  
> +	if (cdns->no_drd)
> +		goto phy_set;
> +
>  	writel(OTGCMD_HOST_BUS_DROP | OTGCMD_DEV_BUS_DROP |
>  	       OTGCMD_DEV_POWER_OFF | OTGCMD_HOST_POWER_OFF,
>  	       &cdns->otg_regs->cmd);
> @@ -218,6 +228,8 @@ void cdns_drd_host_off(struct cdns *cdns)
>  	readl_poll_timeout_atomic(&cdns->otg_regs->state, val,
>  				  !(val & OTGSTATE_HOST_STATE_MASK),
>  				  1, 2000000);
> +
> +phy_set:
>  	phy_set_mode(cdns->usb2_phy, PHY_MODE_INVALID);
>  	phy_set_mode(cdns->usb3_phy, PHY_MODE_INVALID);
>  }
> @@ -234,6 +246,9 @@ int cdns_drd_gadget_on(struct cdns *cdns)
>  	u32 ready_bit;
>  	int ret, val;
>  
> +	if (cdns->no_drd)
> +		goto phy_set;
> +
>  	/* switch OTG core */
>  	writel(OTGCMD_DEV_BUS_REQ | reg, &cdns->otg_regs->cmd);
>  
> @@ -251,6 +266,7 @@ int cdns_drd_gadget_on(struct cdns *cdns)
>  		return ret;
>  	}
>  
> +phy_set:
>  	phy_set_mode(cdns->usb2_phy, PHY_MODE_USB_DEVICE);
>  	phy_set_mode(cdns->usb3_phy, PHY_MODE_USB_DEVICE);
>  	return 0;
> @@ -265,6 +281,9 @@ void cdns_drd_gadget_off(struct cdns *cdns)
>  {
>  	u32 val;
>  
> +	if (cdns->no_drd)
> +		goto phy_set;
> +
>  	/*
>  	 * Driver should wait at least 10us after disabling Device
>  	 * before turning-off Device (DEV_BUS_DROP).
> @@ -277,6 +296,8 @@ void cdns_drd_gadget_off(struct cdns *cdns)
>  	readl_poll_timeout_atomic(&cdns->otg_regs->state, val,
>  				  !(val & OTGSTATE_DEV_STATE_MASK),
>  				  1, 2000000);
> +
> +phy_set:
>  	phy_set_mode(cdns->usb2_phy, PHY_MODE_INVALID);
>  	phy_set_mode(cdns->usb3_phy, PHY_MODE_INVALID);
>  }
> @@ -392,6 +413,19 @@ int cdns_drd_init(struct cdns *cdns)
>  	u32 state, reg;
>  	int ret;
>  
> +	if (cdns->no_drd) {
> +		cdns->dr_mode = usb_get_dr_mode(cdns->dev);
> +		cdns->version = CDNSP_CONTROLLER_V2;
> +
> +		if (cdns->dr_mode != USB_DR_MODE_HOST &&
> +		    cdns->dr_mode != USB_DR_MODE_PERIPHERAL) {
> +			dev_err(cdns->dev, "Incorrect dr_mode\n");
> +			return -EINVAL;
> +		}
> +
> +		return 0;
> +	}
> +
>  	regs = devm_ioremap_resource(cdns->dev, &cdns->otg_res);
>  	if (IS_ERR(regs))
>  		return PTR_ERR(regs);
> @@ -492,6 +526,9 @@ int cdns_drd_init(struct cdns *cdns)
>  
>  int cdns_drd_exit(struct cdns *cdns)
>  {
> +	if (cdns->no_drd)
> +		return 0;
> +
>  	cdns_otg_disable_irq(cdns);
>  
>  	return 0;
> @@ -500,6 +537,9 @@ int cdns_drd_exit(struct cdns *cdns)
>  /* Indicate the cdns3 core was power lost before */
>  bool cdns_power_is_lost(struct cdns *cdns)
>  {
> +	if (cdns->no_drd)
> +		return false;
> +
>  	if (cdns->version == CDNS3_CONTROLLER_V0) {
>  		if (!(readl(&cdns->otg_v0_regs->simulate) & BIT(0)))
>  			return true;
> diff --git a/include/linux/pci_ids.h b/include/linux/pci_ids.h
> index 24cb42f66e4b..a6b9b6f6d8cc 100644
> --- a/include/linux/pci_ids.h
> +++ b/include/linux/pci_ids.h
> @@ -2424,6 +2424,7 @@
>  #define PCI_DEVICE_ID_CDNS_USBSS	0x0100
>  #define PCI_DEVICE_ID_CDNS_USB		0x0120
>  #define PCI_DEVICE_ID_CDNS_USBSSP	0x0200
> +#define PCI_DEVICE_ID_CDNS_UDC_USBSSP	0x0400
>  
>  #define PCI_VENDOR_ID_ARECA		0x17d3
>  #define PCI_DEVICE_ID_ARECA_1110	0x1110
> 
> ---
> base-commit: 17c7841d09ee7d33557fd075562d9289b6018c90
> change-id: 20260508-no_drd_config-ea76d1df87a3
> 
> Best regards,
> --  
> Pawel Laszczak <pawell@cadence.com>
> 
> 

-- 

Best regards,
Peter